There are situations where the need of customizing Liferay behavior concerning email address validation arise. For those cases, creating a custom implementation of com.liferay.portal.security.auth.EmailAddressValidator, deploying as a hook and adding the new property to users.email.address.validator works well.
Once done that, it is challenging to access the same implementation from custom code, because the ability to add a custom EmailAddressValidator is primary for providing a way to change the email address validation in the UserService. It's not for using the validator in plugins, at least not on 6.2.
Since Liferay is providing email address validation, it should be provided in a way that it can be used even in custom code (as the Validator class provides such a way today). So the Validator class should make use of the customizable email address validator and not vice-versa.